1. Field of the Invention
The present invention relates to an ultrasonic fluid measurement instrument that measures flow velocity and flow volume of fluid such as gas and water utilizing the propagation time of ultrasonic waves.
2. Description of the Related Art
The conventional ultrasonic fluid measurement instrument that measures flow volume and the like utilizing the propagation time of ultrasonic waves is provided with a measurement part halfway across the fluid channel to measure the flow velocity of fluid flowing through this measurement part according to the propagation time of ultrasonic waves between ultrasonic transmitter-receivers. The flow volume is obtained by multiplying the flow velocity measured above, by the cross-sectional area of the channel in the measurement part, and by a given correction coefficient.
The most significant element that enables highly accurate measurement for flow volume and the like is a flowing state of fluid in the above-mentioned measurement part. In other words, a turbulent fluid flow in the measurement part causes disruption in ultrasonic propagation, disabling highly accurate measurement.
Under the circumstances, the following arrangement has been devised conventionally as disclosed in Japanese Patent Unexamined Publication No. H09-43015. That is, a measurement part is rectangular with its rectangle cross-section, and the short side is partitioned by partition boards to form plural flat split channels in parallel with the long side. The flat split channels effectively make the fluid flow into a laminar flow, namely a two-dimensional stable flow.
Meanwhile, the measurement part composed of the above-mentioned plural flat split channels is significantly large in width compared to the fluid channel for admitting fluid.
Therefore, the measurement part is connected to the fluid channel through a tapered connection part with a larger width at the downstream side.
As a result, this tapered connection part causes a turbulent flow in the fluid, and thus the fluid becomes resistant to flowing evenly through all the split channels, resulting in decreasing measurement accuracy.
The present invention, aiming at solving such conventional problems, provides an ultrasonic fluid measurement instrument that enables highly accurate measurement of fluid flow.